THEMIS daytime infrared image mosaic of Elysium Planitia. Shield volcanoes in view include Elysium Mons just right of center, Hecates Tholus to the upper right and Albor Tholus to the lower right.
Elysium Planitia, located in the Elysium quadrangle, is the second largest volcanic region on Mars, after Tharsis. It is centered at . The region includes volcanoes, from north to south, Hecates Tholus, Elysium Mons and Albor Tholus. Another large volcano, Apollinaris Mons, lies south of the others. Besides having large volcanoes, Elysium Planitia has several areas with long trenches, called fossa or fossae (plural) on Mars. They include Cerberus Fossae, Elysium Fossae, and Hephaestus Fossae.
A 2005 photo of Elysium Planitia by the Mars Express spacecraft shows what may be ash-covered water ice. The volume of ice is estimated to be 800 km (500 mi) by 900 km (560 mi) in size and 45 m (148 ft) deep, similar in size and depth to the North Sea. The ice is thought to be the remains of water floods and lava flows in the Cerberus Fossae fissures about 2 to 10 million years ago. The surface of the area is broken into 'plates' like broken ice floating on a lake. Impact crater counts show that the plates are up to 1 million years older than the gap material, showing that the area solidified much too slowly for the material to be basaltic lava.
Volcanoes of Elysium Planitia 
Troughs (Fossae) in Elysium Planitia 
Cerberus Fossae, as seen by HiRISE.
Hephaestus Fossae Two Vews, as seen by HiRISE. Picture on right lies to the top (north) of other picture. Fossa (geology) often form by material moving into an underground void.
See also 
- Fossa (geology)
- Geography of Mars
- Geology of Mars
- List of plains on Mars
- List of quadrangles on Mars
- Young, Kelly (2005-02-25). "'Pack ice' suggests frozen sea on Mars". New Scientist. Retrieved 2007-01-30.
- John B. Murray et al., JB; Muller, JP; Neukum, G; Werner, SC; Van Gasselt, S; Hauber, E; Markiewicz, WJ; Head Jw, 3rd et al. (17 March 2007). "Evidence ... for a frozen sea close to Mars' equator". Nature 434 (7031): 352–355. Bibcode:2005Natur.434..352M. doi:10.1038/nature03379. PMID 15772653.
- Google Mars - zoomable map centered on Elysium Planitia, with three main volcanoes visible
- google mars - Cerebrus Fossae fissures
- Elephant face on Mars